Effect of Precursors on the Electrochemical Properties of Mixed RuOx/MnOx Electrodes Prepared by Thermal Decomposition

Abstract

Growing thin layers of mixed-metal oxides on titanium supports allows for the preparation of versatile electrodes that can be used in many applications. In this work, electrodes coated with thin films of ruthenium (RuOx) and manganese oxide (MnOx) were fabricated via thermal decomposition of a precursor solution deposited on a titanium substrate by spin coating. In particular, we combined different Ru and Mn precursors, either organic or inorganic, and investigated their influence on the morphology and electrochemical properties of the materials. The tested salts were: Ruthenium(III) acetylacetonate (Ru(acac)3), Ruthenium(III) chloride (RuCl3·xH2O), Manganese(II) nitrate (Mn(NO3)2·4H2O), and Manganese(III) acetylacetonate (Mn(acac)3). After fabrication, the films were subjected to different characterization techniques, including scanning electron microscopy (SEM), polarization analysis, open-circuit potential (OCP) measurements, electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD) experiments. The results indicate that compared to the others, the combination of RuCl3 and Mn(acac) produces fewer compact films, which are more susceptible to corrosion, but have outstanding capacitive properties. In particular, this sample exhibits a capacitance of 8.3 mF cm−2 and a coulombic efficiency of higher than 90% in the entire range of investigated current densities.

Electrochemical Chlorine Evolution by Bi–Ti Oxide with a Heterojunction on Ir–Ta Oxide: Insights from the Effects of Layer Configurations

“…For the anodes from the precursors with organic ligands and solvent, on the other hand, the peaks of IrO 2 and Ti were weaker and/or broader than the analogues from the inorganic route. The greater viscosity of organic solvent (isopropanol) than aqueous ones could elevate film thickness and coverage of the outer layer under an identical drop casting procedure . This interpretation conformed to the EDS mapping results (Table S1) where the measured atomic fractions of Ir and Ta on Bi x Ti 10–x O y -O were far lower than that of Bi x Ti 10–x O y -I, regardless of the molar fraction of Bi ( x ).…”

“…The greater viscosity of organic solvent (isopropanol) than aqueous ones could elevate film thickness and coverage of the outer layer under an identical drop casting procedure. 28 This interpretation conformed to the EDS mapping results (Table S1) where the measured atomic fractions of Ir and Ta on Bi x Ti 10−x O y -O were far lower than that of Bi x Ti 10−x O y -I, regardless of the molar fraction of Bi (x). It also agreed with the overall greater weights of Bi x Ti 10−x O y -O layers.…”

“…The ohmic resistance comprises the resistances to ion migration in the electrolyte, polarization, and charge migration across the catalytic film . The combined effects can be depicted as resistors in series within equivalent circuits. ,,− In comparison, the charge transfer (polarization) resistance would not contribute to the ohmic resistance significantly in the current interruption method . The uncompensated resistances of Bi x Ti 10–x O y -O anodes overall outweighed the Bi x Ti 10–x O y -I due to the greater thickness ( vide supra ).…”

“…In spite of the resistance of considerably thick Bi x Ti 10– x O y layers, viable charge transport could be enabled by a thermally driven segregation of Ir cations into the upper Bi x Ti 10– x O y matrix . Nevertheless, excessive loadings of Bi x Ti 10– x O y -O layers seriously elevated the uncompensated resistance to exacerbate the ohmic contact role of Ir 7 Ta 3 O z . This side effect could be explained by intrinsic semiconductor properties of TiO 2 , β-Bi 2 O 3 , and Bi 12 TiO 20 .…”

“…21,32,34−36 In comparison, the charge transfer (polarization) resistance would not contribute to the ohmic resistance significantly in the current interruption method. 28 The uncompensated resistances of Bi anodes in 50 mM NaCl solutions with respect to j, generation rate, and CE as figures-of-merit. The applied E a was 2.0−3.0 V NHE that corresponded to cell voltages from 4 to 6 V. The average j during chronoamperometry showed a general trend that coincided with the voltammograms (Figure 3a and b, Table S2), indicating that the charge transfer was insignificantly limited by diffusion of Cl − .…”